1. Field of the Invention
The present invention relates generally to a monopole antenna, and more particularly to a monopole antenna with a spiral structural benefited with increased gain.
2. Description of the Prior Art
Wireless communication devices, such as cellular phones, notebook computers, electronic appliances, and the like, are normally equipped with an antenna that serves as a medium for transmission and reception of electromagnetic signals, such as date, audio, image, and so on. The antenna can be built outside or inside of the devices. Usually, an external antenna is not easily interfered by inner components of the electrical device and can be easily adjusted by user for achieving desired operating performance. Either a monopole antenna or a dipole antenna is a kind of traditional external antenna. The length of a radiating element of a traditional monopole antenna substantially equals to ½ wavelength (λ). While, when used in long distance transmission/reception, general monopole antenna generally has weak gain and undesired operating performance.
Taiwanese Patent No. 560706, issued to Chen on Nov. 1, 2003, disclosed a hybrid antenna comprising a dipole antenna, a helical antenna, and a rod antenna all of which connect to one another in series. The complex antenna improves the gain of the antenna and the communication distance of the antenna is fairly increased. However, the connection area between the dipole antenna and the inner conductor of the feeding line does not have any additional protection. Thus, not only will the connecting area be easily broken, but will also be easily oxidized. Taiwanese Patent No. I276251, issued to Wong et al. on Feb. 1, 2006, discloses a monopole antenna attached on a printed circuit board and having high gain. However, the monopole antenna failed to work in a wide bandwith.
Hence, in this art, a monopole antenna to overcome the above-mentioned disadvantages of the prior art should be provided.